Rework tree APIs to reflect Google style and more const-correctness....

views/controls/button/native_button_gtk.cc

Index: views/controls/button/native_button_gtk.cc
===================================================================
--- views/controls/button/native_button_gtk.cc	(revision 74117)
+++ views/controls/button/native_button_gtk.cc	(working copy)
@@ -238,9 +238,9 @@
 
   // look for the same group and update
   if (is_add && child == this) {
-    View* container = GetParent();
-    while (container && container->GetParent())
-      container = container->GetParent();
+    View* container = parent();
+    while (container && container->parent())
+      container = container->parent();
     if (container) {
       std::vector<View*> other;
       container->GetViewsWithGroup(native_button_->GetGroup(), &other);